Organic, open cell foam materials, their carbonized derivatives, and methods for producing same

ABSTRACT

Organic, small pore area materials (“SPMs”) are provided comprising open cell foams in unlimited sizes and shapes. These SPMs exhibit minimal shrinkage and cracking. Processes for preparing SPMs are also provided that do not require supercritical extraction. These processes comprise sol-gel polymerization of a hydroxylated aromatic in the presence of at least one suitable electrophilic linking agent and at least one suitable solvent capable of strengthening the sol-gel. Also disclosed are the carbonized derivatives of the organic SPMs.

RELATED APPLICATIONS

This application claims priority from U.S. patent application Ser. No.09/809,793, filed, Mar. 16, 2001, and U.S. Provisional PatentApplication Ser. No. 60/195,165, filed Apr. 6, 2000, the disclosures ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates, generally, to organic, open cell foams.More particularly, the present invention relates to organic, small porearea, open cell foams that may be produced in unlimited sizes andshapes. The foams of this invention have structural properties thatprovide sufficient strength to withstand the stresses of manufacture andthus, exhibit minimal degradation (i.e., shrinking and/or cracking).This invention also relates to carbonized-forms of such materials thatare particularly useful in electrical applications. This inventionfurther relates to methods of producing small pore area materials usingsol-gel polymerization processes that do not require the step ofsupercritical drying of the sol-gels.

BACKGROUND OF THE INVENTION

A small pore area material (“SPM”) is a type of foam, which may bethought of as a dispersion of gas bubbles within a liquid, solid or gel(see IUPAC Compendium of Chemical Terminology (2d ed. 1997)).Specifically, and as used herein, an SPM is a foam having a density ofless than about 1000 kilograms per cubic meter (kg/m³) and a small porestructure in which the average pore area is less Than about 500 :m².Average pore area, as used herein, is the average of the pore areas ofat least the 20 largest pores identified by visual examination of imagesgenerated by scanning electron microscopy (“SEM”). These pore areas werethen measured with the use of ImageJ software, available from NIH.

One type of SPM is a low density microcellular material (“LDMM”).Specifically, and as used herein, an LDMM is an SPM having amicrocellular structure in which the average pore diameter is less thanabout 1000 nanometers (nm) which is determined by measuring the averagepore area and then calculating the average pore diameter by using theformula: area=Πr². For example, an average pore area of 0.8:m²corresponds to an average pore diameter of 1000 nm.

Certain LDMMs are known and have been used in a variety of applicationsincluding, but not limited to, thermal barriers and insulation,acoustical barriers and insulation, electrical and electroniccomponents, shock and impact isolators, and chemical applications. See,e.g., Materials Research Society, vol. 15, no. 12 (December 1990);Lawrence Livermore National Labs Materials, Science BulletinUCRL-TB-117598-37; U.S. Pat. No. 4,832,881. For a foam having an averagepore diameter greater than about 300 nm, pore area is the preferablecharacterization of the pores as it can be more easily measured using,e.g., SEM images with available software that calculates pore andparticle size.

The usefulness of any particular foam depends on certain properties,including, but not limited to, bulk density, bulk size, cell or porestructure, and/or strength. See, e.g., “Mechanical Structure-PropertyRelationship of Aerogels,” Journal of Non-Crystalline Solids, vol. 277,pp. 127-41 (2000); “Thermal and Electrical Conductivity of MonolithicCarbon Aerogels,” Journal of Applied Physics, vol. 73 (2), 15 Jan. 1993;“Organic Aerogels: Microstructural Dependence of Mechanical Propertiesin Compression,” Journal of Non-Crystalline Solids, vol. 125, pp. 67-75(1990). For example, density affects, among other things, a foam's solidthermal conductivity, mechanical strength (elastic modulus), and soundvelocity. In general, lowering the density of a foam will also lower itssolid thermal conductivity, elastic modulus, and longitudinal soundvelocity. However, a foam's density cannot be too low otherwise it willnot satisfy the mechanical stability of its intended application.

In addition, a foam will generally be more useful and better suited tomore applications if it can be produced in a variety of shapes andsizes. Further, pore structure affects, among other things, the gaseousthermal conductivity within a foam, as well as mechanical strength andsurface area. In general, smaller pore size (average pore area and/oraverage pore diameter) improves a foam's physical properties in theseareas if the density of the material does not increase. It is thereforedesirable in most cases to lower density and pore size until a minimumis reached for both cases. This can be difficult to achieve since, inmost materials, these properties counteract each other so thatdecreasing density leads to larger pore sizes.

Other important properties, at least for purposes of commercialization,include ease and flexibility of manufacture, for example, the ability towithstand the stresses that typically exist during manufacture thatcause degradation (e.g., shrinkage and/or cracking), and the ability tomake foams having a broad range of properties, sizes and shapes that canalso be made in situ.

Generally, foams can be classified by their pore size distribution.Average pore diameter may fall within three ranges: (1) micropore, inwhich the average pore diameter is less than about 2 nm; (2) mesopore,in which the average pore diameter is between about 2 nm and about 50nm; and (3) macropore, in which the average pore diameter is greaterthan about 50 nm. See IUPAC Compendium of Chemical Terminology (2d ed.1997). An example of a foam having a micropore structure is a xerogel.An example of a foam having a mesopore structure, and a particularlyuseful foam, is an aerogel. Generally, an aerogel is a type of LDMM (andthus it is also an SPM) in which gas is dispersed in an amorphous solidcomposed of interconnected particles that form small, interconnectedpores. The size of the particles and the pores typically range fromabout 1 to about 100 nm. Specifically, and as used herein, an aerogel isan LDMM (and thus it is also an SPM) in which: (1) the average porediameter is between about 2 nm and about 50 nm, which is determined fromthe multipoint BJH (Barrett, Joyner and Halenda) adsorption curve of N₂over a range of relative pressures, typically 0.01-0.99 (“the BJHmethod” measures the average pore diameter of those pores havingdiameters between 1-300 nm and does not account for larger pores); and(2) at least 50% of its total pore volume comprises pores having a porediameter of between 1-300 nm.

Another way to classify foams is by the number of closed or open poresthey have. For example, closed pore foams have a high number of sealedor encapsulated pores that trap the dispersed gas such that the gascannot easily escape. See, e.g., U.S. Pat. Nos. 6,121,337; 4,243,717;and 4,997,706. Open pore foams have a lower number of sealed orencapsulated pores and, as such, the interior spaces and surfaces areaccessible and the gas within them may be evacuated. Thus, foams withmore open pores are more desirable for evacuated thermal insulation,chemical and catalytic reactions, and electrical applications. Forexample, only open pore materials can be evacuated for increased thermalinsulation commonly known as vacuum insulation, many chemical andcatalytic reactions operate by accessing activated surfaces on theinterior of foams thus more open spaces and surfaces increase reactionefficiencies, and many electrical applications also operate by accessingconducting surfaces thus more open surfaces increase electricalefficiencies. In general, the known SPM foams are open pore foams inwhich nearly all the pores are open. Other foams that are not SPMstypically have fewer open pores, in which generally less than about 80%of the pores are open.

SPM foams may be further classified, for example, by the type ofcomponents from which they are made. For example, inorganic aerogelfoams may be made using silica, metal oxides or metal alkoxide materialsand typically exhibit high surface area, low density, opticaltransparency and adequate thermal insulation properties. See, e.g., U.S.Pat. Nos. 5,795,557; 5,538,931; 5,851,947; 5,953,363. However, inorganicaerogels have several problems. For example, the precursor materials arerelatively expensive, sensitive to moisture, and exhibit limitedshelf-life. See, e.g., U.S. Pat. No. 5,525,643. Also, the processes usedto make inorganic aerogels are typically expensive and time-consumingrequiring multiple solvent-exchange steps, undesirable supercriticaldrying (discussed in more detail below) and/or expensive reagents forthe modification of the gel surfaces. See, e.g., “Silica Aerogel FilmsPrepared at Ambient Pressure by Using Surface Derivatization to InduceReversible Drying Shrinkage,” Nature, vol. 374, no. 30, pp. 439-43(March 1995); “Mechanical Strengthening of TMOS-Based Alcogels by Agingin Silane Solutions,” Journal of Sol-Gel Science and Technology, vol. 3,pp. 199-204 (1994); “Synthesis of Monolithic Silica Gels byHypercritical Solvent Evacuation,” Journal of Materials Science, vol.19, pp. 1656-65 (1984); “Stress Development During SupercriticalDrying,” Journal of Non-Crystalline Solids, vol. 145, pp. 3-40 (1992);and U.S. Pat. No. 2,680,696.

In contrast, organic SPM foams typically exhibit lower solid thermalconductivity and can be readily converted into low density, high surfacearea carbonized-foams that exhibit high electrical conductivity.Moreover, the precursor materials used to make organic SPMs tend to beinexpensive and exhibit long shelf-lives. See, e.g., “AerogelCommercialization: Technology, Markets, and Costs,” Journal ofNon-Crystalline Solids, vol. 186, pp. 372-79 (1995). Further, organicSPMs can be opaque (useful to reduce radiative thermal transfer) ortransparent, although such opaque foams do not require opacification. Asa result, generally, opaque organic SPMs are more desirable, especiallyfor electronic applications and thermal applications in which opticaltransparency is not desired.

Foams, including SPM foams, can also be classified by their bulkproperties. Monolithic foams, or monoliths, can be defined as being bulkmaterials having volumes greater than 0.125 mL, which corresponds to ablock of material having a volume greater than 125 mm³ (i.e., 5 mm×5mm×5 mm). Thin film and sheet foams can be defined as a coating, lessthan 5 mm thick, formed on a substrate. Granular or powder foams can bedefined as comprising particle sizes of having volumes less than 0.125mL. In general, foams that can be made in monolithic form haveadvantages over thin film or granular foams. For example, monolithicfoams can be made for a wide variety of applications in which thinfilms, sheets or granulars would not be practical. For example, mostthermal insulation, acoustical attenuation and kinetic (shockabsorption) applications require thicker insulating material that cannotbe provided by thin films or sheets. And, granular materials tend tosettle and are not mechanically stable. Many chemical and catalyticapplications also require more material than can be provided by thinfilms or sheets. Even some electrical applications require monolithicmaterials such as fuel cells and large capacitor electrodes.

In general, organic SPMs made using non-critical drying methods havebeen limited to LDMMs in thin film or granular forms. Organic,monolithic LDMMs generally have not been made using non-critical dryingmethods with one exception which took four days to prepare. See U.S.Pat. No. 5,945,084.

Further, although large monolithic inorganic aerogels have been made,such shapes and sizes have been limited and these inorganic aerogelshave been made using undesirable supercritical drying methods (asexplained below). For example, silica aerogels have been made in thefollowing shapes and sizes: (1) a sheet 1 cm thick and having a lengthand width of 76 cm (corresponding to a volume of 5.776 liters); and (2)a cylinder 12 inches long having a diameter of 8 inches (correspondingto a volume of 9.884 liters).

Organic aerogels made using supercritical drying methods, however, havemuch more limited shapes and sizes, e.g.: (1) a sheet 1 inch thick andhaving a length and width of 12 inches (corresponding to a volume of2.36 liters); and (2) a disk 3 inches thick having a diameter of 8inches (corresponding to a volume of 2.47 liters). No organic monolithicaerogel is known whose smallest dimension is greater than 3 inches.Further, no organic monolithic aerogel is known that is made usingnon-critical drying techniques where the smallest diameter is greaterthan 5 mm. In addition, many of the known organic monolithic foams lacksufficient structural strength to withstand the stresses arising duringmanufacture. As a result, these foams tend to shrink and some also crackduring manufacture.

In general, foams can be made using a wide variety of processes. See,e.g., U.S. Pat. Nos. 6,147,134; 5,889,071; 6,187,831; and 5,229,429.However, aerogels have been typically made using well known “sol-gel”processes. The term “sol” is used to indicate a dispersion of a solid ina liquid. The term “gel” is used to indicate a chemical system in whichone component provides a sufficient structural network for rigidity, andother components fill the spaces between the structural units. The term“sol-gel” is used to indicate a capillary network formed by interlinked,dispersed solid particles of a sol, filled by a liquid component.

The preparation of foams by such known sol-gel processes generallyinvolves two steps. In the first step, the precursor chemicals are mixedtogether and allowed to form a sol-gel under ambient conditions, or,more typically, at temperatures higher than ambient. In the second step,commonly referred to as the “drying step,” the liquid component of thesol-gel is removed. See, e.g., U.S. Pat. Nos. 4,610,863; 4,873,218; and5,476,878. The ability to dry the sol-gel is in part dependent on thesize of the foam. A larger foam will require more intensive dryingbecause of the longer distance the solvent must pass from the interiorof the foam to the exterior. A sol-gel that is dried in a mold orcontainer will require that the liquid travel through the sol-gel to theopen surface of the mold or container in order for the liquid componentto be removed.

Conventional supercritical drying methods usually require theundesirable and potentially dangerous step of supercritical extractionof the solvent. In the case of direct supercritical extraction (aprocess wherein the solvent in which the sol-gel is formed is removeddirectly without exchanging it for another solvent), the solvent that isbeing extracted is most typically an alcohol (e.g., methanol), whichrequires high temperatures and pressures for extraction. Such conditionsrequire the use of highly pressurized vessels. Subjecting alcohols tothe high temperatures and pressures increases the risk of fire and/orexplosion. Methanol poses the additional risk of toxicity.

Known sol-gel processes have several additional problems. In manyinstances, the precursor materials used are expensive and can bedangerous under the conditions used in conventional supercriticaldrying. Also, the resulting foams have been made in limited sizes andshapes due to constraints inherent in the known manufacturing processesand they also tend to exhibit cracking and/or shrinkage.

Another problem with conventional drying methods is that the drying stepis time consuming and frequently quite tedious, typically requiring oneor more solvent exchanges. See, e.g., U.S. Pat. Nos. 5,190,987;5,420,168; 5,476,878; 5,556,892; 5,744,510; and 5,565,142. A furtherproblem is that conventional drying methods sometimes require theadditional step of chemically modifying the sol-gel. See, e.g., U.S.Pat. No. 5,565,142; “Silica Aerogel Films Prepared at Ambient Pressureby Using Surface Derivatization to Induce Reversible Drying Shrinkage,”Nature, vol. 374, no. 30, pp. 439-43 (March 1995).

For example, the most common process for aerogel production involvesexchanging the solvent in which the sol-gel is formed (typically alcoholor water) with liquid carbon dioxide, which is then removed bysupercritical extraction. Although the supercritical extraction ofcarbon dioxide requires relatively low temperatures (under 40° C.), itrequires very high pressures (generally above 1070 psi). And, althoughcarbon dioxide is non-flammable, the solvent-exchange step is very timeconsuming.

Moreover, even the known processes using ambient (non-critical) dryingmethods have deficiencies in that they do not produce low densitymonolithic foams, but rather thin films or granules.

As explained above, the known processes tend to produce organic aerogelshaving limited shapes and sizes. One reason for this is that the mold orcontainer in which the foam is made is limited in size and/or shape. Asa result, such processes do not allow for the extraction of foams wherethe distance the solvent must pass is very large.

An example of a known process for making foams is U.S. Pat. No.5,565,142, which describes certain inorganic foams produced usingevaporative drying methods. The described process requires solventexchange and a further step wherein the sol-gel is chemically modified.Similarly, U.S. Pat. No. 5,945,084 describes the production ofresorcinol foams by evaporative drying processes in which the lowestreported density of these foams is greater than 400 kg/m³. However,these foams exhibit relatively high thermal conductivity and require anexcessive amount of time to gel, cure and dry. One example took morethan four days to complete.

Although known foams may exhibit some of the above-described usefulproperties, no known foam exhibits all of these properties. Thus, anorganic, small pore area, open cell foam that can have a wide variety ofmonolithic forms with sufficient structural strength and that optionallycan be formed in situ is still needed.

SUMMARY OF THE INVENTION

One objective of this invention is to provide organic SPMs comprisinglarge, monolithic foams having sizes that are not limited by the methodin which they are made. The only limit as to the size and shape of thesefoams is the application in which they will be used. By way of exampleonly, the SPMs of this invention can be made in situ in the walls or ininsulated barriers used in refrigerated trucks, buildings, and aircraft.

It is another objective of this invention to provide large, monolithic,organic SPMs with large bulk shapes and sizes whose smallest dimension(e.g., width, height, length, thickness, diameter) is greater than about3 inches; and/or sufficient structural strength to withstand thestresses arising during manufacture such that they are substantiallyfree of cracks.

It is another objective of this invention to provide organic SPMscomprising monolithic foams prepared using non-critical dryingprocesses. Such materials have sufficient structural strength towithstand the stresses arising during manufacture such that they aresubstantially free of cracks.

It is a further objective of this invention to provide organic SPMshaving an average pore area less than about 500 μm². It is anotherobjective to provide organic LDMMs having an average pore diameterbetween about 50 nm and about 1000 nm. This corresponds to an averagepore area of about 2000 nm² to about 0.8 μm². Such SPMs and LDMMs havedensities less than about 300 kg/m³, pore structures in which greaterthan about 80% of the pores are open, and/or low thermal conductivitiesunder vacuum.

Additional objectives include providing carbonized-forms of theabove-described SPMs useful in electronic and chemical applications,among others; providing methods for making these materials, includingmethods that do not require supercritical drying and yet still yieldlarge, monolithic foams.

These objectives are merely exemplary and are not intended to limit thescope of the invention described in more detail below and defined in theclaims.

DETAILED DESCRIPTION OF THE INVENTION

In order that this invention may be more fully understood, the followingdetailed description is set forth. However, the detailed description isnot intended to limit the inventions that are defined by the Claims. Itwill be appreciated by one of skill in the art that the properties ofthe SPMs, as well as the steps and materials used in the manufacture ofsuch materials may be combined and/or varied without departing from thescope of the basic invention as disclosed herein.

Properties of the SPMs

The SPMs of this invention comprise organic foams having unique and/orimproved properties. Such properties include, but are not limited to,low and/or variable densities; pore structures having small pore sizesand/or a large portion of open pores; large monolithic shapes and sizes;sufficient structural strength to withstand the stresses that ariseduring manufacture; low thermal conductivities; and/or the ability to beformed in situ.

As defined above, an SPM is a foam having a density less than about 1000kg/m³ and a pore area less than about 500 μm². As used herein, the termSPM is intended to encompass LDMMs and aerogels. Thus, a reference tothe SPMs of this invention includes, but is not limited to, LDMMs andaerogels. Similarly, the term LDMM is intended to encompass aerogels.Thus, a reference to the LDMMs of this invention includes, but is notlimited to, aerogels.

The SPMs of this invention preferably have a density less than about 500kg/m³, more preferably less than about 300 kg/m³, even more preferablyless than about 275 kg/m³, and yet even more preferably less than about250 kg/m³, and yet further even more preferably less than about 150kg/m³. SPMs, with even lower densities (e.g., less than 100 kg/m³) areespecially preferred because, as discussed in more detail below, 30′they may exhibit additional preferred properties such as lower thermalconductivity.

The SPMs of this invention preferably have average pore areas less thanabout 200 μm². More preferably, the SPMs of this invention have averagepore areas less than about 100 μm², and even more preferably less thanabout 50 μm². SPMs with smaller average pore areas (e.g., less thanabout 0.8 μm² and even smaller, e.g., less than about 2000 nm²) areespecially preferred because, as discussed in more detail below, theymay exhibit additional preferred properties such as lower thermalconductivity.

The LDMMs of this invention preferably have small average porediameters, between about 2 nm and about 1000 nm. More preferably, theLDMMs of this invention have average pore diameters between about 2 nmand 50 nm. LDMMs with small pore diameters (e.g., between about 2 nm andabout 20 nm) are especially preferred because, as discussed in moredetail below, they may exhibit additional preferred properties such aslower thermal conductivity.

The aerogels of this invention preferably have small average porediameters. More preferably, the aerogels of this invention have averagepore diameters between about 2 nm and about 20 nm.

The SPMs of this invention also comprise an open cell structure in whichgreater than about 80% of the cells or pores are open. The amount ofopen pores can be calculated by measuring the absorption of liquidnitrogen or by using standard nitrogen gas adsorption measurements (BETanalysis). In general, the greater the open cell structure of the SPM,the greater the evacuated thermal insulation, chemical, catalytic, andelectrical properties the material exhibits. Thus, preferably, the SPMsof this invention comprise an open cell structure in which at leastabout 90% of the cells or pores are open, and more preferablysubstantially all of the pores are open.

The SPMs of this invention may further comprise monolithic shapes andsizes. Such SPMs have volumes greater than about 0.125 mL in which nosingle dimension is less than about 5 mm. Thus, for example, in the caseof an SPM having a generally rectangular shape, the length, width andheight of the material must each be no less than about 5 mm. Similarly,for generally round, spherical, or elliptical shapes, the smallestdiameter must be no less than about 5 mm. Larger monolithic SPMs of thisinvention, in which no single dimension is less than about 75 mm (3inches), may be formed by using non-critical drying methods. The maximumsize of the SPMs of this invention, however, is not limited and can takeany size, shape or form. For example, the SPMs of this invention can bemade in situ in the walls or insulated barriers used in refrigeratedtrucks, buildings and aircraft.

Such bulk properties differentiate the SPMs of this invention from knownthin film, sheet, granular or powder foams. The limitations of thinfilm, sheet, granular and powder foams are known. For example, mostthermal insulation, acoustical attenuation and kinetic (shockabsorption) applications require an insulating material thicker thanthat provided by thin films or sheets. And, granular materials tend tosettle and are not mechanically stable. Also, many chemical andcatalytic applications require larger shapes (monolithic materials) thanthin films or sheets can provide. Even some electrical applications suchas fuel cells and large capacitor electrodes require monolithicmaterials.

The SPMs of this invention may also have sufficient structural strengthto minimize degradation during manufacture. Thus, for example, theyexhibit substantially no cracking. The SPMs may also exhibit minimalshrinkage (i.e., the final product is nearly the same physical size asthe precursor solution from which it is derived). For example, in thecase of aerogels formed using a sol-gel process, the aerogels of thisinvention exhibit minimal shrinkage compared to the sol-gel. Preferably,the SPMs exhibit less than about 25% shrinkage, and more preferably donot substantially shrink at all.

The enhanced structural strength of these SPMs may be achieved by theinclusion of a suitable solvent that strengthens the solid network by,for example, providing strong hydrogen bonding and/or covalentmodifications within the SPM network. An example of this interactionwould be, in the case of an aerogel, a complex between one or morehydroxylated aromatics and one or more hydrogen-bonding agents. Apreferred solvent is a material that provides strong hydrogen bondingsuch as an aliphatic carboxylic acid, including acetic acid, formicacid, propionic acid, butyric acid, pentanoic acid, and isomers thereof,with acetic acid being most preferred. Thus, the SPMs of this inventioncomprise a hydrogen bonding agent (e.g., acetic acid) to providesufficient structural strength to minimize degradation of the networkduring non-critical drying.

Another unique and/or improved property that may be exhibited by theSPMs of this invention includes low thermal conductivity or thermaltransfer. The lower the thermal conductivity, the better thermalinsulation properties (i.e., lower thermal transfer) the SPM exhibits.Thus, a preferred SPM may exhibit a thermal conductivity of less thanabout 0.0135 watts per meter per Kelvin (W/(m·K)) up to pressures of 10Torr, and even more preferred, less than 0.008 W/(m·K) up to pressuresof 10 Torr. Another preferred SPM may exhibit a thermal conductivity ofless than about 0.009 W/(m·K) up to about 1 Torr, and even morepreferred, less than about 0.007 W/(m·K) up to about 1.0 Torr. And, afurther preferred SPM may exhibit a thermal conductivity of less thanabout 0.005 W/(m·K) up to about 0.1 Torr, and even more preferred, lessthan about 0.0035 W/(m·K) up to about 0.1 Torr. A more preferred SPM ofthis invention exhibiting these thermal conductivities is a monolithicSPM formed using a non-critical drying method.

Additional, and optional, properties of the SPMs of this inventioninclude high surface areas (greater than about 10 m²/g, preferablygreater than about 50 m²/g, more preferably greater than about 100 m²/g,and even more preferably greater than about 200 m²/g, and still evenmore preferably greater than about 300 m²/g); low resistivities (lessthan about 0.02 ohm meter, preferably less than about 0.002 ohm meter);high acoustical impedance; high compressive strength; high shockabsorption; and/or high chemical resistance to minimize solventswelling.

Having described the properties that the SPMs this invention mayexhibit, exemplary embodiments of unique combinations of theseproperties are provided. In one embodiment, an organic SPM of thisinvention

comprises a foam having an average pore area less than about 500 μm²; adensity of less than about 300 kg/m³; and greater than about 80% of thepores are open pores. Preferably, all of the pores are open pores andthe density is less than about 275 kg/m³.

In another embodiment, the organic SPM of this invention is a monolithicstructure that has been non-critically dried and has a thermalconductivity of less than about 0.0135 W/(m·K) up to pressures of 10Torr, and more preferably, less than 0.008 W/(m·K) up to pressures of 10Torr. Another such SPM has a thermal conductivity of less than about0.009 W/(m·K) up to about 1 Torr, and more preferably, less than about0.007 W/(m·K) up to about 1.0 Torr. And, a further such SPM has athermal conductivity of less than about 0.005 W/(m·K) up to about 0.1Torr, and more preferably, less than about 0.0035 W/(m·K) up to about0.1 Torr.

In a preferred embodiment, the organic SPM of this invention comprisesan aerogel foam—defined above as having an average pore diameter ofbetween about 2 nm and 50 nm—that is prepared using non-critical dryingprocesses. This aerogel has a monolithic form while maintainingsufficient structural strength such that it is substantially free ofcracks.

In another preferred embodiment, the organic SPM of this inventioncomprises a monolithic foam whose smallest dimension is greater thanabout 3 inches while maintaining sufficient structural strength suchthat it is substantially free of cracks.

Process of Making Small Pore Area Materials and Low DensityMicrocellular Materials

In general, organic SPMs, including those of the present invention, maybe prepared using an improved two-step sol-gel polymerization process.The first step comprises reacting an hydroxylated aromatic or a polymerresin comprising an hydroxylated aromatic with at least oneelectrophilic linking agent in a solvent. The solvent comprises at leastone compound, which is a liquid that dissolves the organic precursor,precipitates the cross-linked product, and serves to strengthen thesolid network during the second step (i.e., drying). Mechanisms for thisstrengthening interaction may include strong hydrogen bonding and/orcovalent modifications that stiffen the polymer backbone so as tominimize (and preferably prevent) cracking and shrinking during drying.The reaction may take place in the presence of a catalyst that promotespolymerization and/or cross-linking and produces sol-gel formation at arate consistent with or more rapid than rates for other SPMs known inthe art.

The second step, comprises drying the sol-gel to remove the liquidcomponents. Unlike other sol-gel processes, the drying step does notrequire supercritical extraction and/or does not cause substantialdegradation. Although supercritical extraction methods optionally may beused alone or in combination with other drying methods, they are notpreferred.

More particularly, in the first step of the inventive process, thehydroxylated aromatic or polymer resin comprising the hydroxylatedaromatic may be added in an amount from about 0.5% to about 40% (byweight based on the resulting solution), preferably from about 1% toabout 20%, and more preferably from about 1% to about 8%. Theelectrophilic agent may be added in an amount from about 1% to about 40%(by weight based on the resulting solution), preferably from about 3% toabout 20%, and more preferably from about 4% to about 8%. The solventmay be added in an amount from about 30% to about 97% (by weight basedon the resulting solution), preferably from about 50% to about 94%, andmore preferably from about 60% to about 85%.

The precursor chemicals are mixed together and allowed to form a sol-gelin an environment maintained at an ambient pressure and a temperaturebetween about 20° C. and about 100° C., and preferably between about 40°C. and about 80° C. It is believed that such temperatures provide rapidthorough cross-linking of the chemical matrix, which results instronger, higher quality, finished SPMs. The processing temperaturestend to be limited by the boiling point of the precursor chemicalsolution and by the vessel or mold in which the gel is formed. However,if the process is conducted at pressures greater than ambient, then theprocessing temperature may be increased (if a more temperature-tolerantvessel or mold is used).

Further, it is also believed that increasing temperature to the higherend of the range increases the rate of cross-linking, however, it alsoincreases pore size. Whereas, lowering the temperature increases thetime it takes to prepare the sol-gel. Therefore, to form small pores, itmay be desirable to allow gelation to occur at, for example, 40° C.,after which the temperature may be increased, possibly in stages to, forexample, 80° C., to provide the most thoroughly cross-linked, strong andrigid finished product in the least amount of time. As discussed below,other variables may be adjusted or changed to allow for smaller poreswithout the need for incremental temperature increases.

Optionally, the chemical precursors may be preheated prior to gelationto prevent, or reduce, expansion of the pore fluid during gelation andcuring. Furthermore, in order to prevent premature drying of thesol-gel, it is important to ensure that the container within which thegel is formed is capped, of kept pressurized, substantially at all timesprior to the drying step.

According to one drying process methodology, the liquid component of thefinished sol-gel may be removed by evaporative methods. For example, ithas been determined that an evaporation cycle at a reduced (vacuum)pressure and at a temperature of between about 50° C. and 100° C. forabout 2 to about 20 hours, depending upon sample size and formulation,is effective to remove the liquid component of the sol-gel.

According to another drying process methodology, most of the liquidcomponent of the finished sol-gel may be removed by centrifugation, andthe remaining liquid may be removed by evaporative methods. The solidmatrix of the foams of the present invention have been observed to besufficiently strong to withstand processing by centrifugation atapproximately 2000 revolutions per minute (rpm), more preferably up to1000 rpm and even more preferably up to 500 rpm.

According to yet another drying process methodology, most of the liquidcomponent of the finished sol-gel may be removed by applying a pressuredifferential across the sol-gel; thereby, forcing the liquid componentout of the sol-gel by displacing the liquid component with the gas. Thiscan be accomplished by applying gas pressure to one side of the sol-gelwith the other side exposed to atmospheric pressure. Alternatively, areduced pressure (vacuum) can be applied to one side (with the otherside exposed to atmospheric pressure). The remaining liquid may beremoved by evaporative methods, as above. The gas, such as air, also maybe heated in order to speed evaporation.

According to still another drying process methodology, the liquidcomponent of the finished sol-gel may be removed by freeze drying (i.e.,sublimation drying). First, the wet gel is frozen. Next, the gel issubjected to reduced pressure, and the frozen solvent sublimes, orchanges directly from solid to gas without passing through a liquidphase.

A further, and preferred, drying process involves vacuumpurging/flushing the sol-gel using a low surface tension solvent. Thesolvent used to extract the pore fluid should have a surface tensionlower than that of the original solvent used for preparing the sol-gel.First, the low surface tension solvent is supplied to one side of thesol-gel. A pressure differential is then applied across the sol-gel toremove the original pore fluid and force the low surface tension solventthrough the sol-gel. The low surface tension solvent aids in theextraction of the original pore fluid by “washing” it out of, andreplacing it in, the pores. Because the solvent has a low surfacetension, it is more readily extracted from the sol-gel. Suitableflushing solvents include, but are not limited to, hexane, ethyl ether,pentane, 2-methylbutane, acetone, methanol, ethanol, isopropanol, amixture of solvents, or a series of one solvent followed by another. Itis contemplated that the ideal flushing solvent has two properties: (1)a degree of affinity for the pore fluid such that the pore fluid iseffectively removed by the flushing solvent; (2) a surface tension lowenough such that, once the original pore fluid is substantially replacedby the flushing solvent, the flushing solvent is relatively easilyextracted by evaporation; (3) a boiling point low enough such that theflushing solvent is relatively easily extracted by evaporation.Additionally, the low surface tension solvent could be extracted fromthe sol-gel by freeze drying, centrifugation or other methods. It isfurther contemplated that because surface tension decreases astemperature increases, it can be desirable to preheat the low surfacetension solvent and/or the sol-gel. The vacuum purging/flushing methoddescribed above is performed under ambient conditions. Modifications tothis method, such as flushing at elevated pressures, could allow for theuse of additional lower surface tension solvents such as, but notlimited to, butane.

One embodiment for the above-described vacuum purging/flushing dryingprocess involves the production of a hollow cylindrical structurecomprising an SPM of the present invention. In this embodiment, thestructure is formed within a mold comprising an inner cylinder within alarger diameter outer cylinder. At least one end of the mold is capped.

In a preferred process for producing such hollow cylindrical structures(as well as for producing structures of other geometries), it is notnecessary to remove the mold from the sol-gel in order to perform thedrying process. In this process, the mold may become part of thefinished product. After the sol-gel is fully cured, a low surfacetension flushing solvent is introduced at one end of the mold, and, withthe application of a pressure differential, the solvent is drawn throughopenings at the opposite end of the mold. These openings may take theform of ports or holes in the mold, or, alternatively, by totallyremoving the end caps, which provides more surface area, and thereby amore rapid and evenly distributed flow-through of the low surfacetension flushing solvent. As the length of the mold is increased, thedistance between ends of the sol-gel becomes greater, which willincrease the time required for the vacuum purge/flushing drying process.

In another preferred process, the sol-gel cylinder is removed from themold, and the low surface tension flushing solvent is supplied to eitherthe inside or the outside walls of the cylinder. With the application ofa pressure differential, the low surface tension solvent passes throughthe sol-gel. By this method, since the flushing/drying process occursthrough the walls of the structure, the time required for this processis dependent on the thickness of the walls, and does not necessarilyincrease as the length of the cylinder increases. Optionally, thesol-gel may be supported with a perforated sheet or other rigidelement(s) that preferably does not greatly interfere with the flow ofthe low surface tension solvent through the sol-gel.

The inventive processes yield SPMs having a unique and/or improvedcombination of properties including, but not limited to, foams with awide range of densities (e.g., from about 50 kg/m³ to about 500 kg/m³),having open cell structures, in monolithic forms, and/or exhibitingminimal degradation (i.e., shrinkage or cracking) and without apparentsize or shape limitations.

Although sol-gel polymerization processes of an hydroxylated aromaticand an electrophilic linking agent are known, such processes have beenconducted in the absence of a solvent capable of strengthening the gelnetwork. See, e.g., U.S. Pat. Nos. 5,945,084; 5,476,878; 5,556,892; and4,873,218. Such known processes require time-consuming drying protocolsand/or do not yield foams in monolithic forms. This limits their use tothe production of thin films or supporting substrates, or to theproduction of granules or thin wafers. And, although some known sol-gelprocesses have produced unshrunken monolithic gels capable ofwithstanding the pressures induced by non-critical drying, theseprocesses require lengthy drying protocols and yield foams that do noexhibit the unique properties of this invention. See, e.g., U.S. Pat.Nos. 5,945,084; and 5,565,142. Specifically, these materials have higherbulk densities, larger particle and pore sizes, and/or a significantfraction of closed pores within the solid structure. Further, some ofthese known materials cannot be carbonized, and thus, cannot be used inelectrical applications.

Preferably, the hydroxylated aromatics useful in the inventive processesmay be selected from the group comprising phenol, resorcinol, catechol,hydroquinone, and phloroglucinol. More preferably, the hydroxylatedaromatic comprises a phenol compound. Even more preferably, thehydroxylated aromatic comprises part of a soluble polymer resin in whichthe hydroxylated aromatic has been co-polymerized with a linking agentuseful in the inventive processes such as formaldehyde.

Preferably, the electrophilic linking agent useful in the inventiveprocesses may be selected from the group comprising aldehydes andcertain alcohols. More preferably, the aldehyde may be furfural orformaldehyde, and even more preferably, furfural. A suitable alcohol maybe furfuryl alcohol. However, furfural is a more preferred electrophiliclinking agent.

Commonly available, partially pre-polymerized forms of the hydroxylatedaromatic may also be used. For example, liquid phenolic resins may beused, such as FurCarb LP520 (QO Chemicals, Inc., West Lafayette, Ind.)as well as phenolic-novolak resins GP-2018C, GP-5833 and GP-2074, withGP-2018c being more preferred (Georgia-Pacific Resins, Inc., Decatur,Ga.). Those with higher average molecular weights (e.g., GP-2018c)appear to produce the strongest, most rigid finished product. Further,in general and with all other variables being equal, as the molecularweight of the resin increases, the average pore size decreases. Suchproducts are solid flakes which must be dissolved in a liquid solventprior to use in the processes of this invention. Alternatively, a liquidresin may be used such as FurCarb UP520 (QO Chemicals, Inc., WestLafayette, Ind.) which comprises a phenolic-novolak that has beendissolved in an approximately equal weight amount of furfural. In thatcase, the liquid resin comprises not only the hydroxylated aromatic butalso, the electrophilic linking agent. Preferably, however, thesolid-form of the phenolic resin material is used because it allows moreflexibility for adjustment of the phenol/furfural ratio, a variable thataffects the properties of the finished product. Where pre-polymerizedforms of the hydroxylated aromatic and electrophilic linking agents areused (e.g., phenolic-novolak flakes), the ratio of novolak/furfuralshould be adjusted to maximize the amount of cross-linking betweenphenolic-novolak and furfural and to minimize the cross-linking offurfural to itself. It is contemplated that each cross-link uses afurfural molecule and a phenolic novolak site. For a given novolak,there is a certain amount of sites available to cross-link, and as such,it would be desirable to provide a sufficient amount of furfural toachieve as complete cross-linking as possible but without providing toomuch excess. Under certain conditions, if too much furfural is used itmay cross-link to itself forming a furfural foam having inferiorproperties.

Preferably, the solvent comprises a reactive compound acting as both ahydrogen-bond donor and acceptor capable of interacting with multiplesites on the polymer backbone. Suitable solvents include aliphaticcarboxylic acids. More preferably, the solvent is selected from thegroup consisting of acetic acid, formic acid, propionic acid, butyricacid, pentanoic acid, and isomers thereof, with acetic acid being evenmore preferred.

Without wishing to be bound by any particular theory, it is believedthat, in the case of a solvent comprising a hydrogen-bonding solvent,the solvent dissolves the precursor, precipitates the cross-linkedproduct, and forms hydrogen-bonded adducts with the hydroxylatedaromatics in the backbone of the cross-linked product. Thishydrogen-bonding interaction involves two or more hydroxylated aromaticsand constitutes an additional cross-linking mechanism, resulting in amore robust sol-gel which is relatively more tolerant of stresses fromevaporative, centrifugal, gas pressure, or vacuum drying methods thanare prior art sol-gels.

A catalyst may also be used in the preparation of the sol-gel. Thecatalyst promotes polymerization and produces sol-gel formation at arate consistent with or more rapid than other SPMs known in the art.See, e.g., U.S. Pat. Nos. 5,556,892 and 4,402,927. Examples of preferredcatalysts that may be used include mineral acids, such as, but notlimited to, hydrochloric acid, hydrobromic acid, sulfuric acid, andLewis acids, such as, but not limited to, aluminum trichloride and borontrifluoride. More preferred catalysts include hydrochloric acid,hydrobromic acid and sulfuric acid. In general, increasing the amount ofcatalyst substantially reduces the time required for gelation and/orcuring. However, increasing the amount of catalyst may also increasepore size.

Although the mineral acids are preferred, other commercially availablecatalysts having similar chemical properties, for example QUACORR2001″catalyst (QO Chemicals, Inc., West Lafayette, Ind.), may also beused. It will be recognized by one ordinarily skilled in the art that acompatible catalyst in accordance with the present formulation willincrease the rate of the electrophilic aromatic substitution reactionconstituting the cross-linking process above the rate exhibited in theabsence of the catalyst. It has been found in relation to the presentformulations that increased amounts of catalyst, for example, up toapproximately seven percent (7%) by total weight of the sample for someformulations, increases hardness of the resulting solid matrix; but alsoincreases average pore size within the resulting organic foam.

The reaction mixture may also include other suitable agents to enhancecertain useful properties of the SPMs or to assist in the reaction. Forexample, optional alcohol may be added to reduce the average pore sizewithin, and to increase the strength of, the resulting organic SPMs. Theamount of the optional alcohol to be added to the reaction mixture ispreferably between about 3% and about 13% (by weight of the totalmixture).

The effect of adding alcohol or increasing the alcohol content is a veryuseful and pronounced means of reducing pore size. However, adding orincreasing alcohol content also tends to increase gelation time. But,the effect of alcohol may be used in combination with adjustments orchanges to other variables to offset the undesirable effects. Forexample, it may be desirable to increase the gelation and/or curingtemperature (or increase the amount of acid catalyst) while at the sametime increasing the alcohol content. In this way, it is believed thatthe increased alcohol content will more than offset the larger pore sizecaused by the increased temperature (or increased amount of acidcatalyst). And, the increased temperature (or increased amount of acidcatalyst) will offset the longer gelation time caused by the increasedalcohol content.

There may be, however, a maximum allowable amount of alcohol that can beadded to a particular formulation that is processed at a particulargelation temperature. If more than this maximum allowable amount ofalcohol is added, the pore size becomes too small and the sol-gel mayshrink during the drying step.

Examples of useful alcohols include aliphatic alcohols and polyalcohols.Preferred aliphatic alcohols include ethyl, 1- or 2-propyl, some butyls(not t-butyl), and most pentyl alcohols, with isopropanol being morepreferred due to its low toxicity and because it is relativelyinexpensive. Preferred polyalcohols include ethylene glycol, propyleneglycol and glycerine. Polyalcohols tend to form SPMs with very smallpore size. However, polyalcohols tend to be more difficult to extract byevaporation (but may be more readily extracted by solvent purgingtechniques described below), and they tend to produce gels that shrinkwhen dried. Accordingly, aliphatic alcohols are more preferred.

The reaction mixture may also include surfactants to further reduce, orprevent, shrinkage upon drying, presumably by reducing the surfacetension of the pore fluid, thereby making extraction of the pore fluid(i.e., the drying step) easier, especially when dried by evaporativeprocesses. The surfactant allows for the production of unshrunkenmonoliths with smaller pore sizes than is possible without the use ofthis component while maintaining the same unshrunken characteristic.However, depending on the processing conditions, some amount of thesurfactant may remain after removal of the pore fluid. Thus, for someapplications (e.g., applications for insulation), it may not bedesirable to use a surfactant in which case, other variables (e.g.,material formulation and/or processing parameters) should be adjusted toavoid shrinkage (without resorting to the use of surfactants). Forexample, where the SPM is pyrolized to form a carbonized-derivativeuseful in electrical applications, surfactants may be useful because anyresidual surfactant will be removed during pyrolysis.

Examples of useful surfactants include low molecular weight, non-ionic,primary alcohol ethoxylates. One such family of surfactants is NEODOL(Shell Chemical Company, Houston, Tex.), such as NEODOL 23-3 and NEODOL23-5. Tergitol XL-80N or Tergitol 15-S-7 (Union Carbide Co.) is anotherexample that may also be used.

If desired, doping agents, as known and defined in the prior art, may beadded to chemically activate the foam. Examples of useful dopantsinclude metal powders, metal oxides, metal salts, silica, alumina,aluminosilicates, carbon black, fibers, and the like. See, e.g., U.S.Pat. Nos. 5,476,878 and 5,358,802.

Further, additives comprising novoloid fibers (organic polymers madefrom phenol and formaldehyde and available from American Kynol,Pleasantville, N.Y.) may be used to further strengthen the SPM. Suchnovoloid fiber additives may provide structural strength to the gel, andallow for the preparation of lighter, less dense materials than can bemade without the fibers. Because novoloid fibers are compatible with thebase resins of the present invention, the gels may cross-link to thenovoloid fibers, forming a coherent matrix. Additionally, the novoloidfibers can be completely pyrolized into a carbonized form compatiblewith the pyrolized foams of the present invention.

It is contemplated that the fibers can be added in such a way that theysettle and produce a very hard base at the bottom of the finished foamthat can be used for mechanical attachment to other devices. Also thegels can be slowly rotated so that the fibers are evenly distributedthroughout the sol-gel or the fibers can be added when the viscosity ofthe sol-gel is high enough to prevent the fibers from settling.

Fire resistant additives may also be added. Typically, flame-retardingchemicals are based on combinations of bromine, chlorine, antimony,boron, and phosphorus. Many of these retardants emit afire-extinguishing gas (halogen) when heated. Others react by swellingor foaming, forming an insulation barrier against heat and flame.Accordingly, one such exemplary fire retardant useful in the presentinvention is 2,3-dibromopropanol.

Although the formulations described herein produce SPMs with noobservable shrinkage (i.e., the final product is substantially the samephysical size as the sol-gel from which it is derived), if theformulations are not balanced correctly, the SPMs will shrink during thedrying process. The factors that affect the tendency to shrink are theoverall strength of the sol-gel and the sizes of the pores therein. Thestrength of a foam is related to density (i.e., all other variablesbeing equal, a higher density foam will be stronger than a lower densityfoam). The tendency of the sol-gel to shrink upon drying is related topore size (i.e., all other variables being equal, a foam with smallerpores will be more prone to shrinkage than one with larger pores). Thus,a sol-gel with a relatively strong and well-formed solid capillarynetwork has less tendency to shrink upon drying, and a sol-gel withmicropores has more tendency to shrink upon drying.

The formulation may be tailored to obtain the desired mix of properties.For many applications, the ideal material is a relatively strong, rigidfoam which is also of a relatively low density, and also has relativelysmall pore sizes. Oftentimes, therefore, when producing the organic SPMsof the present invention, the goal is to maximize strength and rigidityof the SPM material while, at the same time, producing a relativelylow-density product, and further minimizing pore size such that thepores are of the smallest diameter that will still permit production ofan unshrunken product.

In the case where the SPM is to be used in a thermal insulationapplication, lowering density and/or reducing pore size may decreasethermal conductivity or thermal transfer. In general, there are threetypes of thermal transfer: solid conduction, gas conduction andradiative conduction. See, e.g., “Thermal Properties of Organic andInorganic Aerogels,” Journal of Materials Research, vol. 9, no. 3 (March1994), incorporated by reference herein. Low density porous materials,such as SPMs, typically have low solid conduction. SPMs with higherdensity generally have higher solid conduction. Opaque SPMs alsotypically have low radiative conduction. As the SPM becomes moretransparent, radiative conduction increases. A preferred SPM of thisinvention is black, which does not use an opacifier, in order to reduceradiative conduction.

To achieve an SPM with useful thermal insulation properties, it isdesirable to minimize gas conduction. Gas conduction is produced mostlyby gas molecules transferring heat to one another when they collide,thereby transferring heat from the “hot side” to the “cold side” of athermal insulator. One way to eliminate gas conduction is to completelyremove all of the gas (e.g., keeping the SPM under high vacuum).However, because this is not practical, it is desirable that the SPMhave low conduction without resorting to high vacuum. This can beachieved by making the average pore diameter smaller and preferably lessthan the mean free path or MFP (i.e., the average distance a gasmolecule must travel before it collides with another gas molecule) at agiven pressure.

At ambient pressures, the MFP is quite short and it becomes moredifficult to produce an SPM that has low gas conductivity with thedistance between opposing surfaces of the pores smaller than the MFP.However, as pressure is lowered, the MFP becomes longer and SPMs can bemade more easily with pore sizes smaller than the MFP. The SPMs of thepresent invention exhibit very low gas thermal conductivity at pressuresbelow about 10 Torr.

However, although smaller pore size is generally desirable to achievelower thermal conductivity, the amount of time and effort required forfluid extraction (drying) increases. Further, with all things equal,smaller pore size may increase the risk of shrinkage.

The processes according to the present invention allow for theproduction of SPMs having small pore sizes (diameters) and small averagepore areas with minimal shrinkage. For example, the above describedvacuum purge process can be used on a commercial scale to yieldunshrunken monoliths with smaller pores than is practical on acommercial scale with evaporative drying. When evaporative drying is tobe used, the presence of a surfactant in the formulation facilitatesdrying and yields unshrunken monoliths. Thus, the formulation and/orprocessing conditions are tailored to obtain the desired mix ofproperties.

Density can be altered, and thus thermal conductivity can be altered, byusing formulations that have a lower or higher solid content. At ambientconditions, SPMs with lower density have lower solid conduction, and gasconduction dominates. Thus, SPMs with higher density typically havelower overall thermal conductivity at ambient conditions. At lowpressure, neglecting radiative heat transfer, solid conduction ispredominant and gas conduction is negligible neglecting radiative heattransfer. Thus, when gas conduction is mostly eliminated by lowering thegas pressure by evacuation, lower density SPMs exhibit lower overallthermal conductivity than high density SPMs.

Density can also be altered to alter pore sizes and thus, average poreareas. With all other variables being equal, higher density generallyresults in smaller pores. However, higher density SPMs require moreprecursor chemicals and are therefore more expensive to produce. Thus,the formulation and/or processing condition must be tailored to achievea good balance between density, pore size (average pore diameter andaverage pore area), cost and thermal conductivity.

A preferred formulation used to prepare an SPM of this inventioncomprises (all in weight %) from about 70% to about 80% acetic acid (asthe solvent); from about 5% to about 11% isopropyl alcohol, “IPA” (as anadditive); from about 2% to about 7% hydrobromic acid (as the catalyst),from about 4% to about 8% novolak (as the hydroxylated aromatic); andfrom about 2% to about 7% furfural (as the electrophilic linking agent).An even more preferred formulation comprises 77% acetic acid, 7%isopropyl alcohol, 5% hydrobromic acid, 6% novolak and 5% furfural. Analternative preferred formulation comprises sulfuric acid instead ofhydrobromic acid as the catalyst.

The isopropanol component of the above formulation may be replaced, withno obvious change in the finished material, by an equal amount of1-propanol or an approximate molar equivalent (1.1 g) of ethanol. Otheralcohols may also be used with success.

Increasing the acid component of the above-described formulationproduces, up to a point, stronger materials. As an example, ifhydrobromic acid is used, it can be increased up to about seven percent(7%) by weight without any obvious deleterious effect (e.g., reactionoccurs too quickly and yields large particles and pores and may producea gel that is cosmetically inferior), although above a certain amount,the tendency to produce stronger gels diminishes. Hydrochloric acid,which is less expensive, may be used in place of the hydrobromic acid,but the resultant SPM materials have larger pores than those producedusing hydrobromic acid. Sulfuric acid may also be used and produces gelsthat are relatively strong and rigid. However, in the case of some glassor plastic molds, the use of sulfuric acid may interfere with theability to form a sol-gel. There are methods to overcome this, such as,but not limited to, pretreating the glass or plastic mold with sulfuricacid.

It may now be seen by one ordinarily skilled in the art that variationswithin the above-described process parameters, including but not limitedto those of formulation, temperature, and drying methods, may result inSPMs having controlled average pore size and improved solid networkstrength that can be tailored to meet the needs of the application. SuchSPMs may be formed into large, uncracked, net shaped monoliths.

The SPMs of this invention, including those formed by theabove-described improved procedures, can be further processed. Forexample, the SPMs may be pyrolized to yield carbon foams. Suchcarbonized foams have particularly useful electrical properties. Forexample, carbonized foams exhibit low electrical resistance and areelectrically conductive. By virtue of their high surface areas, suchSPMs have exceptional charge-storing capacities. Any of the well knownpyrolysis processes can be used. See, e.g., U.S. Pat. No. 5,744,510.

Additionally, in the case where the SPMs are formed in a standardizedshape, the SPMs may be readily cut, machined, or otherwise formed toadjust the shape of the monolith to fit the application. Preferably, theSPMs of this invention are formed in situ within a cast or mold in avariety of shapes and/or sizes to fit the final product exactly. Underthese circumstances, the SPM should exhibit substantially no shrinkagesuch that upon in situ formation, the SPM maintains the dimensions ofthe application. Thus, for example, where the SPM is being formed insitu in walls or insulated barriers (e.g., used in refrigerated trucks,buildings, or aircraft), the formed SPM should substantially occupy thespace within the walls or insulated barriers.

In order that this invention may be better understood, the followingexamples are set forth.

EXAMPLES

Samples of the SPMs of this invention were prepared using a sol-gelpolymerization process. As discussed above, the sol-gel process involvesthe formation of a continuous solid matrix within a liquid solvent. Inthis process the solvent is subsequently removed, leaving the driedsolid matrix behind. The observed facile removal of this liquid from thesamples that were prepared by the methods discussed below indicates thatthe solvent-filled pores within the solid network are open andaccessible to the atmosphere. Thus the SPMs that were prepared hadcontiguous networks of open cells which comprised more than about 80%,and substantially 100%, of the open pores in the solid.

The specific process by which they were made, and the precursormaterials used, are described below. Unless otherwise indicated, each ofthe SPMs that was prepared had the following dimensions: a cylinder 25mm long with a 36 mm diameter (25.5 mL). Also, each of the SPMs that wasprepared was black except for those Examples using resorcinol or novolakcross-linked with formaldehyde.

After the samples were prepared, they were subjected to a series ofanalytical tests and/or visually examined. The analytical tests aredescribed below in more detail. Visual examinations included, forexample, whether the SPM exhibited any shrinkage; whether the top of theSPM was flat or concave; whether and to what extent the top of the SPMwas pushed inward (a quick approximation and relative measure of thestrength and rigidity); and whether and to what extent the SPM, uponbreaking, left a clean or cleaved break at the fracture point.

In general, each of the samples was prepared using one of the dryingmethods shown in Table 1 below (unless otherwise indicated). The totalamount of time required to prepare the samples (gelation, curing anddrying) was less that about 24 hours, with the exception of some of thesamples prepared using Method I. As one of skill in the art willappreciate, in the examples dried using Method I, the time required todry the samples can be reduced using other drying methods hereindescribed.

TABLE 1 Drying Methods Method No. Drying Method I Enhanced Evaporation:the sample is placed in a vacuum oven at between 40° C. to 80° C., andunder a vacuum of about 50 Torr, until the sample is dried tocompletion. II Centrifugation: most of the pore fluid is removed bycentrifugation at 500 rpm for 10 minutes, after which the sample isdried to completion by evaporation as described in Method I. IIIVacuum-Induced Pressure Differential: the sample is formed in a bottleor tube, and a reduced pressure of about 500 Torr is applied to one sideof sample. Most of the pore fluid is removed in about 15 minutes, afterwhich the sample is dried to completion by evaporation as described inMethod I. IV Pressure-Induced Pressure Differential: the sample isformed in a bottle or tube, and gas pressure of less than about 10 psiis applied to one side of sample. Most of the pore fluid is removed inabout 20 minutes, after which the sample is dried to completion byevaporation as described in Method I. V Vacuum Purge/Flushing: thesample is formed in a bottle or tube, and a reduced pressure of about500 Torr is applied to one side of sample, while a low surface tensionsolvent is applied to the opposite side of the sample. The sample ismostly dried in about 15 minutes and completely dried in about one hour.

Examples 1-12, as shown on Tables 2 and 3 below, were prepared and driedaccording to Method I of Table 1. Duplicate preparations (“a”) ofExamples 1-12 were dried using the vacuum purge/flushing method, MethodV, in which pentane was used as the lower surface tension solvent forthe flushing step. The vacuum purge/flushing drying method was not usedfor Examples 1, 2, 7 and 11 (Table 3)

TABLE 2 Exam- Wt % Wt % Wt % % ple Acetic Wt % Wt % Wt % Wt % Fur- 2018CSol- Number Acid IPA H₂SO₄ HCl HBr fural resin ids 1 70.0 8.0 7.0 7.08.0 15 2 70.0 11.0 7.0 5.0 7.0 12 3 75.0 11.0 7.0 3.0 4.0 7 4 73.0 5.07.0 7.0 8.0 15 5 80.0 5.0 2.0 6.0 7.0 13 6 80.0 5.0 7.0 3.5 4.5 8 7 80.011.0 2.0 3.0 4.0 7 8 80.0 8.0 5.0 3.0 4.0 7 9 77.0 7.0 5.0 5.0 6.0 11 1077.0 7.0 5.0 5.0 6.0 11 11 77.0 7.0 5.0 5.0 6.0 11 12 80.0 8.0 5.0 3.04.0 7

TABLE 3 BJH % Average Volume Average Com- Skeletal Bulk % Surface Pore %of Pore pression Drying Density Density Open Area Diameter 1-300 nm Areaunder Example Method (g/cm³) (kg/m³) Space (m²/g) (nm) Pores (μm²) loadCategory  1 I 1.4926 214 86 191 17 39 1.0 1 SPM  2 I 1.4963 390 74 23310 61 0.1 4 aerogel  3 I 1.5340 157 90 45 37  1 67 47 SPM  3a V 1.6700101 94 3 16  1 61 44 SPM  4 I 1.5105 269 82 160 22 24 4 4 SPM  5 I1.5915 167 90 56 23 36 0.1 4 LDMM  5a V 1.6749 146 91 23 23 21 19 4 SPM 6 I 1.5265 157 90 13 8  2 191 45 SPM  6a V 1.7390 113 94 2 10  1 175 47SPM  7 I 1.4832 91 94 42 27 21 0.8 37 LDMM  8 I 1.5774 115 93 8 49   0.596 SPM  8a V 1.7223 95 94 1 24  1 183 52 SPM  9 I 1.5399 145 91 38 21 204 6 SPM  9a V 1.7972 144 92 16 29 13 34 5 SPM 10 I 1.6422 129 92 66 3692 4 4 SPM 10a V 1.5978 133 92 68 19 43 16 9 SPM 11 I 1.5630 140 91 19019 144* 0.2 4 aerogel 12 I 1.5795 151 90 82 33 82 1 17 SPM 12a V 1.6021110 93 69 19 50 22 21 SPM *This corresponds to a maximum 100%.Table 3 shows several physical characteristics of Examples 1-12. All ofthese examples are SPMs. As shown, some examples can be furthercharacterized as LDMMs and aerogels. This demonstrates a range ofphysical properties that can be achieved by varying the formulation ofthe sol-gel. The materials vary in their mechanical strength, fromnearly incompressible to 50% compression under load, compare Example 1to Example 8. The surface area of Examples 1-12 vary from 1 to almost200 m²/g.

Table 3 also shows that the SPMs of this invention, including thosefurther characterized as LDMMs and aerogels, have greater than 70% openspace, which is defined as that fraction of the foam's total volume notoccupied by the solid network.

Examples 13-17, as shown in Table 4 below, were prepared using a liquidphenolic-furfural resin (FurCarb) for the hydroxylated aromatic andelectrophilic linking agent components. These formulations were mixed in60 mL plastic bottles, and produced 30 gram samples. The alcohol (wherepresent) was mixed with the acetic acid, the FurCarb was then dissolvedin the acetic acid solution, and the acid was then slowly added withmixing. The bottle was then capped and hand shaken for about one minute.The sample was then placed in a 60° C. oven for 6 to 8 hours, afterwhich the pore fluid was removed by the specified drying method.

TABLE 4 Formulations with liquid resin Example Number Component (wt %)13 14 15 16 17 Acetic Acid 81.1 81.1 81.1 81.1 76.1 FurCarb UP-520* 13.513.5 13.5 13.5 14.1 Isopropyl Alcohol 0 0 0 0 4.2 Hydrochloric Acid 5.45.4 5.4 5.4 5.6 Method of Pore Fluid Removal I II III IV I Average PoreArea, :m² 40.4 15.7 17.2 8.1 4.3 *phenolic-novolak dissolved in anequivalent amount (by weight) of furfural

Examples 13-17 are SPMs. Based on the examination of the resultingfoams, it was observed that the addition of alcohol produced higherquality foams of greater rigidity and smaller pore diameter as comparedto formulations that did not contain alcohol.

Examples 18-39, as described in Tables 5-9 below, were prepared using asolid phenolic-novolak flake-resins. These formulations were mixed inplastic bottles. The alcohol component was added to the acetic acid,then the acid catalyst was added, followed by gentle mixing. Thesurfactant component (if present) was then added, followed by the resin,followed by the cross-linking agent (furfural or formaldehyde). Thebottle was then capped and hand shaken for about one minute. The samplewas then placed in a 40° C. gelation oven for 8 hours, then transferredto an 80° C. curing oven for 8 hours, after which the pore fluid wasremoved by Method I as described above.

TABLE 5 Formulations with solid phenolic-novolak flake resin ExampleNumber Component (wt %) 18 19 20 21 22 Acetic Acid 77.3 74.8 78.7 75.680.6 GP-2056 7.4 GP-2074 7.8 GP-5833 7.4 GP-2018C 6.1 6.1 IsopropylAlcohol 6.7 6.7 3.3 6.7 5 Hydrochloric Acid 6.7 Hydrobromic Acid 3.3 6.73.3 3.3 Furfural 5.3 2.3 7.3 5 5 Formaldehyde (37% aqueous) 1.7 AveragePore Area, :m² 0.4 12 1.3 1.2 0.3 Volume % of 1-300 nm 30 3 23 43 58Average Pore Diameter, 13 9 13 14 13 nm of 1-300 nm Pores

Examples 18-22 are SPMs which were prepared using several differentphenolic-novolak flake resins from Georgia Pacific, listed above fromthe lowest to highest average molecular weight. Examples 18 and 22 arefurther characterized as LDMMs, based upon their average pore areasbeing less than about 0.8 :m², which correspond to average porediameters of less than about 1000 nm. Example 22 is also characterizedas an aerogel, based upon its average pore diameter (of pores havingdiameters between 1-300 nm) being between 2-50 nm (13 nm) and that suchpores constitute more than 50% of the overall pore volume.

TABLE 6 Formulations with solid phenolic-novolak flake resin ExampleNumber Component (wt %) 23 24 25 26 Acetic Acid 80.2 78.9 77.6 77.6GP-5833 novolak flake resin 6.1 6.1 6.1 6.1 Ethyl alcohol 3.7 N-PropylAlcohol 5 1-Butyl Alcohol 6.3 Isobutyl Alcohol 6.3 NEODOL 23-5 1.7 1.71.7 1.7 Hydrobromic acid 3.3 3.3 3.3 3.3 Furfural 5 5 5 5

TABLE 7 Formulations with solid phenolic-novolak flake resin ExampleNumber Component (wt %) 27 28 29 Acetic Acid 78.9 78.9 78.9 GP-5833novolak flake resin 6.1 6.1 6.1 1-Pentanol 5 Iso-amyl alcohol 5Cyclohexanol 5 NEODOL 23-5 1.7 1.7 1.7 Hydrobromic acid 3.3 3.3 3.3Furfural 5 5 5

TABLE 8 Formulations with solid phenolic-novolak flake resin ExampleNumber Component (wt %) 30 31 32 33 Acetic Acid 78.9 78.9 78.9 78.9GP-5833 6.1 6.1 6.1 6.1 2-Ethoxy-ethanol 5 (cellosolve) Ethylene Glycol5 Propylene Glycol 5 Glycerol 5 NEODOL 23-5 1.7 1.7 1.7 1.7 Hydrobromicacid 3.3 3.3 3.3 3.3 Furfural 5 5 5 5

Examples 23-33 were prepared using several different alcohol additives.In general, all of these formulations produced good, monolithic foamsthat were unshrunken with the exception of the samples prepared usingpolyalcohol (Examples 31-33), which exhibited shrinkage. Examples 23-30are believed to be SPMs because they have compositions similar to, andwere prepared using gel/cure conditions similar to those used for,Example 11, (which is an SPM, and is further characterized as anaerogel). In addition to qualitative comparisons made between Examples23-30 and Example 11, the differences in compositions between theseexamples are not believed to have increased the average pore area togreater than 500 :m². In addition, Examples 31-33 are also believed tobe SPMs because these examples exhibited shrinkage, which would haveproduced pores even smaller than Examples 23-30.

TABLE 9 Formulations with solid phenolic-novolak flake resin ExampleNumber Component (wt %) 34 35 36 37 38 39 Acetic Acid 74 70 77.5 79.380.7 78.9 GP-2018C novolak 0 0 0 5 4.3 6.1 flake resin GP-2074 novolak8.9 13.3 0 0 0 0 flake resin GP-5833 novolak 0 0 6.1 0 0 0 flake resinIsopropyl alcohol 6.7 0 0 5 5 5 Glycerol 0 0 6.7 0 0 0 Tergitol XL-80N 00 0 1.7 1.7 0 Hydrobromic acid 6.7 0 0 5 5 0 Hydrochloric acid 0 10 6.70 0 0 Sulfuric acid 0 0 0 0 0 3.3 Furfural 0 0 3 4 3.3 5 Formaldehyde3.7 0 0 0 0 0 (aqueous, 37%) Furfuryl Alcohol 0 6.7 0 0 0 0 Neodol 23-50 0 0 0 0 1.7 Average Pore Area, :m² 0.06 11.6 21 109 61

Examples 34-39 are formulations that resulted in unshrunken monolithicSPMs having a good appearance and rigidity. Examples 35-39 are SPMs, andExample 35 is further characterized as an LDMM, based upon its averagepore area being less than 0.8 :m² (0.06 :m²), which corresponds to anaverage pore diameter of less than about 1000 nm. In addition, Example34 is believed to also be an SPM because its composition is similar to,and it was prepared using gel/cure conditions similar to that used for,Example 19 (which is an SPM). Although Example 34 did not use additionalfurfural as in Example 19, this is not believed to have increased theaverage pore area to greater than 500 :m².

Examples 40-45, as described in Table 10 below, where prepared using thesame process that was used to prepare Examples 18-39, except that thephenolic resin component was replaced by either a non-phenolic resin(Example 40) or a monomeric hydroxylated aromatic (Examples 41-45).

TABLE 10 Formulations with a non-phenolic resin or a monomerichydroxylated aromatic Example Number Component (wt %) 40 41 42 43 44 45Acetic Acid 91.2 81.3 70.3 69.9 77.3 77 B-19-S resorcinol 3.1 0 0 0 0 0flake resin* Resorcinol 0 4 0 0 0 7.3 Hydroquinone 0 0 7.3 0 0 0 Phenol(crystalline) 0 0 0 6.7 3.7 0 Isopropyl Alcohol 0 5 5 5 5 3.3 NEODOL23-5 0 1.7 1.7 1.7 1.7 1.7 Hydrobromic Acid 0 1 5 5 5 0 Sulfuric Acid 10 0 0 0 0 Furfural 4.7 7 0 0 0 0 Furfuryl Alcohol 0 0 0 0 7.3 0Formaldehyde 0 0 10.7 11.7 0 10.7 (37% aqueous) Average Pore Area, :m²12.8 0.1 3.4 241 130.6 0.01 *Indspec Chemical, Pittsburgh, PA

Examples 40-45 are SPMs which were prepared using a variety ofhydroxylated aromatics other than phenolic resins. In addition, Examples41 and 45 are further characterized as LDMMs, based upon their averagepore areas being less than 0.8 :m² (0.1 and 0.01 :m², respectively);which corresponds to average pore diameters of less than about 1000 nm.

It was observed that although Examples 40-45 produced suitablemonoliths, formulations using phenolic resins resulted in higher qualitymaterials. The monomeric resorcinol formulations (Examples 41 and 45)produced well-formed sol-gels which shrank and cracked upon drying. Theother formulations exhibited little or no shrinkage or cracking.

Example 42 was also tested using the BET method to determine its surfacearea. Analyses showed that its surface area was greater than about 300m²/g.

Examples 46-51, as described in Table 11 below, were prepared using thesame process that was used to prepare Examples 18-39 except that theywere gelled and cured at a single temperature for 8 hours total, afterwhich the pore fluid was removed by solvent-flushing with hexane and avacuum-induced pressure differential.

TABLE 11 Formulations processed using solvent-flushing drying techniqueExample Number Component (wt %) 46 47 48 49 50 51 Acetic Acid 75.6 74.374.9 73.6 75.2 74 GP-2018C novolak 6.1 5 6.1 5 6.1 5 flake resinIsopropyl Alcohol 8.3 11.7 7.3 10.7 7 10.3 Sulfuric Acid 5 5 6.7 6.7Hydrobromic Acid 6.7 6.7 Furfural 5 4 5 4 5 4 Temperature of 70 70 60 6060 60 Gelation/Curing Average Pore Area, :m² 7.5 0.5

Examples 46-51 are formulations that resulted in unshrunken monoliths.These formulations are believed to be SPMs because they havecompositions similar to, and were prepared using gel/cure conditionssimilar to those used for, Examples 3, 4 and 9 (each of which is anSPM). Further average pore area measurements of Examples 49 and 50 haveconfirmed that they are SPMs (and that Example 50 is an LDMM) and that acomparison to the Examples in Table 3, based on composition andgel/curing conditions is valid. These SPMs did not have any visualdefects, i.e., the monoliths did not shrink and did not crack, and therate of fluid flow through the samples indicated that they had verysmall pore sizes similar to that exhibited by Example 63 describedbelow. Also, this drying technique produced dried samples faster thanany of the other drying methods used.

Examples 52-53, as shown in Table 12 below, were prepared by gelling theformulation at 40° C. for 8 hours and then curing at 60° C. for 8 hours,followed by drying using Method I. These Examples demonstrate that theprocesses of this invention can be used to prepare SPMs that have a widerange of properties, including bulk densities.

TABLE 12 Formulations Resulting In Relatively High Density Foams Ex. No.Component (wt %) 52* 53 Acetic Acid 71.7 47.8 GP-2018C novolak flakeresin 12 28 Isopropyl Alcohol 5 0 Hydrobromic Acid 3.3 1.5 Furfural 822.7 Bulk Density (mg/cc) 238 510 *Example 52 exhibited about 16%shrinking during drying, thus, substantially increasing density.

Examples 52 and 53 are believed to be SPMs. These examples havecompositions similar to, and were prepared using gel/cure conditionssimilar to those used for, Examples 11 and 12, respectively (which areSPMs). Further, Examples 52 and 53 are believed to have smaller averagepore areas compared to Examples 11 and 12 because Examples 52 and 53have higher densities, which is expected to produce smaller porosities.

Examples 54-56, as shown in Table 13 below, were prepared using the sameprocess that was used to prepare Examples 18-39. Each of these sampleshad a solids content of 11% and a density of about 110 kg/m³. Thesesamples were then subjected to solid state ¹³C NMR spectrometry. Thistest is designed to detect the presence of organic molecules containingthe ¹³C isotope, which is naturally occurring in an abundance ofapproximately 1.1%. This technique provides information on the organiccompounds in the dried gel and the structural features comprising thegel network; specifically, NMR can provide information on the bondingpatterns responsible for the presence of a particular molecule.

TABLE 13 NMR Analyses Example Number 54 55 56 Component (wt %) AceticAcid 78.9 81.6 85.6 GP-2018C 6.1 6.1 0 GP-5833 0 0 6.1 Isopropyl Alcohol5 5 0 NEODOL 23-5 1.7 0 0 Hydrobromic Acid 3.3 3.3 3.3 Furfural 5 5 5NMR Analysis (wt %) in Dried SPM Acetic Acid 4-6 6-8 6-8 NEODOL 23-5 1-2Furfural (unreacted) 1-3 Furfural (cross-linked) 12-18 10-15

Examples 54-56 are believed to be SPMs because they have compositionssimilar to, and were prepared using gel/cure conditions similar to thoseused for, respectively Examples 39, 22 and 20 (which are SPMs). Inaddition to qualitative comparisons made between these examples, thedifferences in compositions and/or process conditions (e.g., the use ofhydrobromic acid in Example 54 instead of sulfuric acid in Example 39,and the lack of IPA in Example 56) are not believed to have increasedthe average pore area to greater than 500 :m².

These Examples show that acetic acid is retained in the dried gel, evenafter extended drying. This suggests that it is strongly anchored to thenetwork by hydrogen-bonding, or it would have evaporated during drying.This is consistent with the hypothesis that acetic acid strengthens thegel by way of the hydrogen-bonding mechanism.

Examples 54-55 show no evidence of the incorporation of isopropanol.Isopropanol is known to be a weaker hydrogen-bonding species than isacetic acid, and it is more easily removed by evacuation.

Example 54 used the surfactant NEODOL; the presence of this material isindicated in the NMR spectrum, confirming that NEODOL remains in thedried sol-gel. Surfactants are desirable for the production of the largemonolithic gels described in Examples 37-39 (used Tergitol XL-80N) and29-33 (used NEODOL 23-5), and the NMR data for Example 54 confirm thepresence of the surfactant in the dried gel. Since resonances for theNEODOL overlap with those of cross-linked furfural, it proved impossibleto quantify the amount of the latter. However, the spectra clearly showthe presence of NEODOL in Example 54.

Examples 57-61, as shown in Table 14 below, were prepared using the sameprocess that was used to prepare Examples18-39. These Examples arebelieved to be SPMs. Examples 57, 60 and 61 have compositions similarto, and were prepared using gel/cure conditions similar to those usedfor, respectively Examples 17, 22 and 9 (which are SPMs). In addition,Examples 58-59 have compositions similar to, and were prepared usinggel/cure conditions similar to those used for, Example 11 (which is anSPM). In addition to qualitative comparisons made between theseexamples, the differences in compositions and/or process conditions(e.g., the addition of Neodol in Example 60) are not believed to haveincreased the average pore area to greater than 500 :m².

The foams that were produced in Examples 57-61 were then pyrolized toproduce carbonized-derivatives, particularly useful in electricalapplications. Specifically, the foams were placed into a ceramic tube,which was then sealed and purged for several hours with argon gas. Thetube was then placed in a high temperature tube oven which wasprogrammed as follows: heat from 22° C. to 250° C. in 2 hours; dwell at250° C. for 4 hours; heat from 250° C. to 1050° C. in 9.5 hours; anddwell at 1050° C. for 9.5 hours.

As can be seen in Table 14, the carbonized-derivatives exhibited volumelosses of between about 48-56%, and mass losses of about 51-67%.Shrinkage is expected from pyrolysis. However, the SPMs of thisinvention exhibited a considerable improvement over the prior art, whichtypically exhibit more than about 70% shrinkage.

TABLE 14 Carbonized-Derivatives Example Number Composition (wt %) 57 5859 60 61 Acetic Acid 83.5 78.9 80.2 78.9 78.9 GP-2018C 6.1 6.1 GP-58336.1 6.1 FurCarb UP-520 13 Isopropyl Alcohol 0.9 5 5 5 Ethyl Alcohol 3.7NEODOL 23-5 1.7 1.7 1.7 1.7 Hydrochloric Acid 2.6 Hydrobromic Acid 3.33.3 3.3 Sulfuric Acid 3.3 Furfural 5 5 5 5 Bulk Density before 110 148100 119 177 carbonization (mg/cc) Bulk Density after 112 108 90 118 127carbonization (mg/cc) Volume Shrinkage (%) 52 55.3 51.0 55.9 48 MassLoss (%) 51.5 67.5 56.0 56 63.2 Resistivity (ohm meter) 0.013 0.0150.017

Examples 62 and 63, shown in Table 15 below, were also prepared and arebelieved to be SPMs. Examples 62 and 63 have compositions similar to,and were prepared using gel/cure conditions similar to those used for,respectively, Examples 17 and 11 (both of which are SPMs). In additionto qualitative comparisons made between these examples, the differencesin compositions and/or process conditions (e.g., using drying Method IVfor Example 63) are not believed to have increased the average pore areato greater than 500 :m².

TABLE 15 Example Number Composition (wt %) 62 63 Acetic Acid 67.6 78GP-2018C 6.1 FurCarb UP-520 14.1 Isopropyl Alcohol 8.4 5 NEODOL 23-5 1.7Hydrochloric Acid 9.9 Hydrobromic Acid 4.2 Furfural 5 Bulk Density(mg/cc) 140 110 Average Pore Diameter 12 41 (nm) of 1-300 nm PoresSurface Area (m²/g) 66 40

Examples 64-72, as shown in Tables 16-17 below, were prepared and arebelieved to be SPMs. Examples 64-66 were prepared using the same processthat was used to prepare Examples 13-17 (which are SPMs), and then driedusing Method I. (See Table 16 for specific comparisons.) Examples 67-71were prepared using the same process that was used to prepare Examples18-39 (which are, or are believed to be, SPMs). (See Table 16 forspecific comparison.) In addition to qualitative comparisons madebetween these examples, any differences in compositions and/or processconditions are not believed to have increased the average pore area togreater than 500 :m².

Examples 64-72 were tested to determine their thermal conductivities.Prior to determining its thermal conductivity, Example 67 (which was cutusing a band saw from the sample prepared in Example 73) was heated inan oven at 100° C. for 5 hours to remove residual surfactant.

TABLE 16 Thermal Conductivity Analyses Example Number Composition (wt %)64 65 66 67 68 Composition Similar 13 17 17 11 12 to Example Acetic Acid77.4 76.0 67.6 78 0 GP-2018C 0 0 0 6.1 5 FurCarb UP-520 14.1 14.1 14.1 00 Isopropyl Alcohol 0 4.2 8.4 5 5 Hydrochloric Acid 8.5 6.7 9.9 0 0Hydrobromic Acid 0 0 0 4.2 3.3 Furfural 0 0 0 5 4.1 Bulk Density (mg/cc)140 140 140 84 91 W/m · K @ Torr * 0.0053 @ 0.017 0.0028 @ 0.004 0.0016@ 0.006 0.0050 @ 0.080 0.0016 @ 0.054 W/m · K @ Torr * 0.0070 @ 0.1000.0035 @ 0.100 0.0036 @ 0.100 0.0060 @ 0.425 0.040 @ 760  W/m · K @Torr * 0.0088 @ 0.800 0.0065 @ 1.00  0.007 @ 1.00 0.0070 @ 1.00  W/m · K@ Torr * 0.0132 @ 10.0  0.0135 @ 10.0  0.0161 @ 10.0  W/m · K @ Torr *0.041 @ 760  0.0445 @ 760  0.062 @ 760  * thermal conductivity in Wattsper meter-Kelvin at given pressure in Torr.

TABLE 17 Thermal Conductivity Analyses Example Number Composition (wt %)69 70 71 72 Composition Similar 11 11 11 11 to Example Acetic Acid 67.677.4 80.6 80.6 GP-2018C 0 7.9 6.1 6.1 FurCarb UP-520 14.1 0 0 0Isopropyl Alcohol 8.4 5 5 5 Hydrochloric Acid 9.9 0 0 0 Hydrobromic Acid0 3.3 3.3 3.3 Furfural 0 6.4 5 5 Density (mg/cc) 144 179 123 112 W/m · K@ Torr * 0.004 @ 0.676 0.0043 @ 0.070 0.0025 @ 0.080 0.005 @ 0.028 W/m ·K @ Torr * 0.004 @ 0.980 0.030 @ 760  0.037 @ 760  0.005 @ 0.040 W/m · K@ Torr * 0.008 @ 10.0  0.05 @ 760  W/m · K @ Torr * 0.039 @ 760  *thermal conductivity in Watts per meter-Kelvin at given pressure in Torr

Example 73, as shown in Table 18 below, was prepared using the sameprocess that was used to prepare Examples 18-39, except that thechemicals were mixed in 1000 ml bottles, then combined in a 8.3 literRubbermaid® storage container, which was filled to slightly more thanabout half full. The resulting foam was an unshrunken, monolithic SPMhaving the following dimensions: 6.2 cm×23 cm×34 cm.

Also, from the same chemical mixture, a smaller sample was prepared(Example 63). As shown in Table 15, that sample (and thus Example 73)had a density of 110 mg/cc; an average pore diameter of 41 nm determinedby the BJH method; and a surface area of 40 m²/g.

TABLE 18 Large, Monolithic Aerogel Ex. No. Composition (wt %) 73 AceticAcid 78 GP-2018C 6.1 Isopropyl Alcohol 5 Hydrobromic Acid 4.2 NEODOL23-5 1.7 Furfural 5 Bulk Density, (mg/cc) 112 Average Pore Area, :m² 1.1

Examples 74 and 75, as shown in Table 19 below, were prepared using thesame process that was used to prepare Example 18-39. Examples 74 and 75are believed to be SPMs. Example 74, which is also believed to be anLDMM, has a composition identical to, and was prepared using the samegel/cure conditions as those used for, Example 22 (which is an SPM, andis further characterized as an LDMM). In addition, Example 75 has acomposition similar to, and was prepared using gel/cure conditionssimilar to those used for, Example 22. The addition of Neodol is notbelieved to have increased the average pore area to greater than 500:m². These Examples show that by adding a surfactant to the formulation,shrinkage can be considerably reduced or eliminated.

TABLE 19 Example Number Composition (wt %) 74 75 Acetic Acid 80.6 78.9GP-2018C 6.1 6.1 Isopropyl Alcohol 5 5 NEODOL 23-5 0 1.7 HydrobromicAcid 3.3 3.3 Furfural 5 5 Shrinkage of dried 20 0 material (vol. %)

Characterization Techniques

Pore area was measured using images of the surface of the materialswhich were obtained by a Topcon model 701LaB6 scanning electronmicroscope (SEM). The materials can be examined as is because they areelectrically conductive, i.e., they were not sputter coated with Au orcarbon. The pore area was then determined using particle size analysissoftware, specifically ImageJ available from NIH.

Bulk density was measured using a disk of material ca. 2.5 cm diameter×1cm thickness. Calipers were used to measure the dimensions of the disk,and the mass was measured with a balance to ±0.001 g. The skeletaldensity (or “true” density) was measured using a Micromeritics Accupyc1330 Helium pycnometer and ultra-high purity (UHP) He. A sample cup ofdimensions about 0.70 inches diameter×1.5 inches depth was used, andsamples were weighed to ±0.00005 g on a Mettler balance. The skeletaldensity and bulk density are used to calculate the percentage of openspace of the materials, typically>90%.

Surface area and pore volume were measured using a Micromeritics Tristar3000 instrument equipped with Smart Prep degassing unit. UHP N2 gas wasused for the analysis. The samples were degassed under flowing drynitrogen at 200° C. for at least 20 hrs, up to 72 hrs. Samples wereweighed after the degas treatment to ±0.001 g. A 5 point BET (BrunauerEmmett Teller) calculation was used to determine the surface area of thematerials. The cumulative pore volume and average pore diameter werecalculated from the multipoint BJH (Barrett, Joyner and Halenda)adsorption curve of N₂ over a range of relative pressures, typically0.01-0.99. This pore volume calculation includes only pores that are1.7-300 nm in diameter. Using the cumulative pore volume from BJH andthe skeletal density, one can determine the percentage of the totalvolume that the 1.7-300 nm diameter pores comprise.

Pore areas have been used to describe and characterize the SPMsdiscussed herein. When comparing the present materials to othermaterials, the reported pore diameter should be converted to a pore area(Area=Πr²).

The relative mechanical strength of the materials was measured usingdisks of each sample of approximately 2.5 cm diameter×1 cm thickness.The sample was placed in a stainless steel holder fitted with astainless steel cylinder which rested on top of the sample disk. Thesample was subjected to 17 inches Hg vacuum for 5 minutes, and thecompression of the material while under vacuum was measured. Thepermanent deformation of the sample was also measured using calipers.

Thermal conductivity was measured using two techniques: hot wire andsteady-state thin heater. In the hot wire technique, cylindrical samplesof SPM were made with a 0.001 inch diameter tungsten wire running thelength of the cylinder. The samples were typically 2.0 cm in diameterand 5.0 to 7.0 cm in length. The samples were then placed within avacuum chamber and measurements of the current through and voltage forthe wire were made as a function of applied power. The resistance of thewire, and hence the temperature of the wire, were then calculated andgraphed as a function of time and fit to theoretical models. Thermalconductivity was then calculated from fit functions. See, e.g. “Thehot-wire method applied to porous materials of low thermalconductivity,” High Temperature High Pressures, 1993, vol. 25, pp.391-402, 13th ECTP Proceedings pp 219-230. In this fashion, thermalconductivities were calculated as a function of pressure.

In the steady-state thin heater technique, a 0.04 cm thick 4.5 cm squareheater is sandwiched between two 1 cm thick×6 cm diameter SPM samples.Thermocouples are placed on the interior and exterior surfaces of thesamples. Aluminum heat sinks are then used to hold the samples andheater together and eliminate any gap between the samples. Thermalconductivity is then calculated by fitting both the temperature increaseand decrease versus time curve as the heater is powered to thermalequilibrium and then turned off. See e.g. ASTM C1114-00. As in the hotwire technique, the samples are put into a vacuum chamber during thesemeasurements so that the thermal conductivity can be calculated as afunction of pressure.

As described above, materials exhibiting both low density andmicrocellular open porosity have many favorable physical properties. Thetests and measurements reported in this application indicate that thematerials disclosed herein exhibit both of these characteristics. Inaddition, the materials disclosed herein can be produced in a widevariety of shapes and sizes, and the process may be completed in timeframes shorter than those reported for prior art materials.Additionally, the current application discloses new compositions ofmatter and formulation processes that use less expensive startingmaterials and easier processing conditions than those describedpreviously.

While particular materials, formulations, operational sequences, processparameters, and end products have been set forth to describe andexemplify this invention, such are not intended to be limiting. Rather,it should be noted by those ordinarily skilled in the art that thewritten disclosures are exemplary only and that various otheralternatives, adaptations, and modifications may be made within thescope of the present invention. Accordingly, the present invention isnot limited to the specific embodiments illustrated herein, but islimited only by the following claims.

All references cited within the body of the instant specification arehereby incorporated by reference in their entirety.

1-67. (canceled)
 68. A method for removing fluid from a sol-gelcomprising the steps of: (a) forming a solution; (b) allowing saidsolution to form a sol-gel; (c) adding a low surface tension solvent tothe sol-gel; (d) applying a pressure differential across the sol-gel;(e) removing substantially all of the original pore fluid portion ofsaid sol-gel; and (f) removing the low surface tension solvent.
 69. Amethod for preparing an organic, low density microcellular material,said method comprising the steps of: (a) forming a solution; (b)allowing said solution to form a sol-gel; (c) adding a low surfacetension solvent to the sol-gel; (d) applying a pressure differentialacross the sol-gel; (e) removing substantially all of the original porefluid portion of said sol-gel; and (f) removing the low surface tensionsolvent.
 70. A method for preparing an organic, low densitymicrocellular material, said method comprising the steps of: (a) forminga solution comprising a hydroxylated aromatic, an electrophilic linkingagent, and a hydrogen-bonding agent; (b) allowing said solution to forma Sol-gel; (c) adding a low surface tension solvent to the sol-gel; (d)applying a pressure differential across the sol-gel; (e) removingsubstantially all of the original pore fluid portion of said sol-gel,and (f) removing the low surface tension solvent.
 71. A method forpreparing an organic, small pore area material, said method comprisingthe steps of: (a) forming a solution; (b) allowing said solution to forma sol-gel; (c) adding a low surface tension solvent to the sol-gel; (d)applying a pressure differential across the sol-gel; (e) removingsubstantially all of the original pore fluid portion of said sol-gel,and (f) removing the low surface tension solvent.
 72. A method forpreparing an organic, small pore area material, said method comprisingthe steps of: (a) forming a solution comprising a hydroxylated aromatic,an electrophilic linking agent, and a hydrogen-bonding agent; (b)allowing said solution to form a sol-gel; (c) adding a low surfacetension solvent to the sol-gel; (d) applying a pressure differentialacross the sol-gel; (e) removing substantially all of the original porefluid portion of said sol-gel, and (f) removing the low surface tensionsolvent.
 73. The method according to any one of claims 68-72, whereinsaid low surface tension solvent is an organic solvents with surfacetension lower than that of the solvent used in preparing the sol-gel.74. The method according to any one of claims 68-72, wherein said lowsurface tension solvent is selected from the group consisting of hexane,ethyl ether, pentane, isopentane, acetone, methanol, ethanol andisopropanol.
 75. The method according to any one of claims 68-72,wherein said low surface tension solvent comprises a hexane compound.76. The method of claim 70 or 72, wherein said hydroxylated aromaticcomprises a hydroxylated benzene compound.
 77. The method of claim 70 or72, wherein said hydroxylated aromatic comprises a phenolic novolakcompound.
 78. The method of any one of claims 68-72, wherein said lowsurface tension solvent is removed by evaporation, freeze drying orcentrifugation.
 79. The method of claim 70 or 72, wherein saidelectrophilic linking agent comprises an aldehyde.
 80. The method ofclaim 70 or 72, wherein said electrophilic linking agent comprisesfurfural.
 81. The method of claim 70 or 72, wherein saidhydrogen-bonding agent comprises a carboxylic acid.
 82. The method ofclaim 70 or 72, wherein said hydrogen-bonding agent comprises aceticacid, formic acid, propionic acid, butyric acid, pentanoic acid or anisomer thereof.
 83. The method of claim 70 or 72, wherein saidhydrogen-bonding agent comprises acetic acid. 84-139. (canceled) 140.The method of any one of claims 69-72, further comprising the step (g)of pyrolizing said material at a pyrolysis temperature to form acarbonized derivative of said material.
 141. The method of claim 70 or72, wherein said electrophilic linking agent comprises alcohol.
 142. Themethod of claim 70 or 72, wherein said alcohol is furfuryl alcohol. 143.The method of claim 70 or 72, wherein the solution formed in step (a)further comprises a catalyzing agent.
 144. The method of claim 143,wherein said catalyzing agent is independently selected from the groupconsisting of hydrochloric acid, sulfuric acid and hydrobromic acid.145. The method of claim 70 or 72, wherein the solution formed in step(a) further comprises a surfactant.
 146. The method of any one of claims68-72, wherein step (b) includes the substep of subjecting said solutionto either: (i) a temperature or a pressure higher than ambient; or (ii)a temperature and a pressure higher than ambient.